Blow mold for molding a container

ABSTRACT

A blow mold is disclosed. The mold includes a pair of mold halves having an operative configuration wherein the mold halves together define a cavity for a container, the container having a main body and a characteristic selected from the group of characteristics consisting of: a push-up base; an integral finish; and an embossed or a debossed feature. Each of the pair of mold halves has a first portion and a second portion formed integrally with the first portion. When the pair of mold halves is in the operative configuration, the first portions collectively define the main body and the second portions collectively define the characteristic. At least one of the pair of mold halves has a relatively soft substrate portion and a relatively hard surface layer formed integrally with the substrate portion.

This application is a continuation-in-part of U.S. application Ser. No. 12/276,434, filed Nov. 24, 2008, which is a continuation-in-part of U.S. application Ser. No. 11/676,371, filed Feb. 19, 2007. Further, this application claims the benefit under 35 U.S.C. §119 of U.S. Provisional Application No. 61/366,740, filed Jul. 22, 2010, the disclosures of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to the field of blow molding.

BACKGROUND OF THE INVENTION

Blow molding is a process commonly used for producing hollow plastic objects. A typical blow molding operation involves mold halves which are closed about an extruded parison of warm plastic and the introduction of air into the closed-off parison to cause same to conform to the shape of the mold cavity. After the plastic has cooled, the mold halves are separated to release a molded product. The mold halves are typically provided with interior conduits through which heat carrying medium is circulated, to heat or cool the mold as necessary in the particular application.

Containers for consumer products are often provided with features such as finishes (threaded necks which receive caps) and “push-ups” or “Champagne” bases (hollows formed in the bases of the containers to provide stability). Historically, portions of the mold halves which define these features in the finished container are defined by inserts which are machined separately from the remainder of the mold and then secured thereto.

Inserts are also used to apply details such as dates, logos and codes to the surface of the molded product, to achieve small variations in the shape of the molded product without the requirement of manufacturing an entirely new mold and, when machined out of harder material than the remainder of the mold, to provide enhanced wear resistance to portions of the mold that can benefit therefrom.

By segmenting the mold halves, mold cavities of very complex shapes can be routinely constructed using conventional three-dimensional milling machinery, as is generally available in mold-making shops.

SUMMARY OF THE INVENTION

Forming one aspect of the invention is a blow mold. The blow mold comprises a pair of mold halves having an operative configuration wherein said mold halves together define a cavity for a container. The container has a main body and a characteristic selected from the group of characteristics consisting of: a push-up base; an integral finish; and an embossed or a debossed feature. Each of the pair of mold halves has a first portion and a second portion formed integrally with the first portion. When the pair of mold halves is in the operative configuration, the first portions collectively define the main body and the second portions collectively define the characteristic. At least one of the pair of mold halves has a relatively soft substrate portion and a relatively hard surface layer formed integrally with the substrate portion.

According to another aspect of the invention, the substrate portion can be an aluminum alloy and the surface layer can be a metal-matrix composite (MMC).

According to another aspect of the invention, the MMC can comprise an aluminum-nickel alloy matrix having WC particles embedded therein.

According to another aspect of the invention, the WC particles can be distributed in the aluminum-nickel alloy matrix in an amount in a range of from 5 wt % to 50 wt %, based on the weight of the composite.

According to another aspect of the invention, the WC particles can be distributed in the aluminum-nickel alloy matrix in an amount in a range of from 10 wt % to 40 wt %, based on the weight of the composite.

According to another aspect of the invention, the WC particles can be distributed in the aluminum-nickel alloy matrix in an amount in a range of from 20 wt % to 35 wt %, based on the weight of the composite.

According to another aspect of the invention, the WC particles can be distributed in the aluminum-nickel alloy matrix in an amount of about 27 wt %, based on the weight of the composite.

According to another aspect of the invention, the aluminum-nickel alloy matrix can comprise Al-12Si alloy alloyed with nickel.

According to another aspect of the invention, the MMC can comprise 1.5-5.4 wt % Ni, based on weight of the composite.

According to another aspect of the invention, the MMC can comprise 2.4-3.6 wt % Ni, based on weight of the composite.

According to another aspect of the invention, the MMC can comprise 3 wt % Ni, based on weight of the composite.

According to another aspect of the invention, the aluminum alloy can be Al 2024 all, Al 2124 all, Al 2219 T31 though T87, Al 6009 all, Al 6010 all, Al 6061 all, Al 6061 T4 through T6511, Al 7075 T6 through T7351, Al 7050 all or Al 7475 all.

According to another aspect of the invention, the aluminum alloy can comprise Al 7075-T6 through T7351.

According to another aspect of the invention, the aluminum alloy can be Al 7075-T651.

A process of producing a mold half forms another aspect of the invention. This process comprises: applying a layer of a metal-matrix composite (MMC) to a piece of machined aluminum alloy to form a composite structure; and machining the composite structure.

According to another aspect of the invention, the MMC can be an aluminum-nickel alloy matrix having WC particles embedded therein.

According to another aspect of the invention, the MMC layer can be formed by laser cladding.

According to another aspect of the invention, the WC particles can be distributed in the aluminum-nickel alloy matrix in an amount in a range of from 20 wt % to 35 wt %, based on the weight of the composite; the aluminum-nickel alloy matrix can comprise Al-12Si alloy; the MMC can comprise 1.5-5.4 wt % Ni, based on weight of the composite; and the aluminum alloy can be Al 7075-T6 through T7351.

According to another aspect of the invention, the composite structure can be machined into the mold half.

According to another aspect of the invention, one or more inserts can be secured to the machined composite structure to form the mold half.

Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter being briefly described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a blow-mold according to a preferred embodiment of the invention, the mold being shown in an operative configuration thereof;

FIG. 2 is a view along section 2-2 of FIG. 1, showing the pin half of the mold;

FIG. 3 is a view along section 3-3 of FIG. 1, showing the bush half of the mold;

FIG. 4 is a side view of a molded precursor product produced with the mold of FIGS. 1-3;

FIG. 5 is a view similar to FIG. 4 of the product of FIG. 4 trimmed for use;

FIG. 6 is an end view of the product of FIG. 5;

FIG. 7 is a bottom view of the product of FIG. 5;

FIG. 8 is a top view of the product of FIG. 5;

FIG. 9 is a schematic drawing of one embodiment of a one-piece blow mold half pre-machined to an undersized shape at the pinch-off and other feature areas;

FIG. 10 is a schematic drawing of one embodiment of a metal-matrix composite (MMC) layer integrated on to the mold half of FIG. 9 at the pinch-off area, where FIG. 10A shows the MMC layer with an initial excess of MMC material and FIG. 10B shows the MMC layer after being machined to final dimension;

FIG. 11 is a schematic drawing of a one-piece blow mold half of the present invention having a metal-matrix composite layer integrated at the pinch-off and other feature areas;

FIG. 12 depicts microstructure of a cross-section of a Al 7075-T651 substrate clad with a Al 4047+30% (90% WC+10% Ni) metal-matrix composite layer;

FIG. 13 depicts a graph showing hardness depth profile of Al 4047+30% (90% WC+10% Ni) metal-matrix composite layer clad on Al 7075-T651 substrate;

FIG. 14 depicts a graph comparing Vickers hardness of Al 4047+30% (90% WC+10% Ni) metal-matrix composite layer to that of Al 7075-T651, A2 steel, Be—Cu alloy and Stainless Steel Stavex ESR; and,

FIG. 15 depicts a graph comparing wear loss of Al 4047+30% (90% WC+10% Ni) metal-matrix composite layer to that of Al 7075-T651, A2 steel, Be—Cu alloy and Stainless Steel Stavex ESR.

DETAILED DESCRIPTION

An exemplary blow-mold constructed according to the preferred invention is illustrated in FIGS. 1-3 and designated with general reference numeral 20. This blow-mold 20 comprises a pair of mold halves 22A,22B. As illustrated, each half 22A,22B includes a first portion 24A,24B, a second portion 26A,26B, a third portion 28A,28B and a fourth portion 29A,29B.

Although not shown, it should be understood that, in use, these mold halves 22A,22B are fitted to a conventional blow molding machine, of the type which extrudes a parison of warm plastic material, and the halves 22A,22B are closed around the parison so as to provide a quantity of warm plastic material having a void in the cavity. Thereafter, air is introduced via a needle or blow pin into the void to conform the material to the shape of the cavity, the material is permitted to cool and harden to produce a molded article 30 as shown in FIG. 4 and the mold is opened to release the article. With the exception of the construction of the mold itself, all of the foregoing is conventional and as such is neither described in detail nor illustrated.

The article 30 will be seen to be a precursor product, with waste flash 30′ which is trimmed in a conventional manner to produce a prototype container 32 as shown in FIGS. 5-8 having a main body 34 defined by the first portions 24A,24B of the mold 20, a push-up base 38 defined by the second portions 28A,28B of the mold 20, an integral threaded finish 36 defined by the third portions 26A,26B of the mold 20 and an embossed feature 31 defined by the fourth portions 29A,29B.

This mold 20 differs from molds of the prior art, in that each mold half 22A,22B is machined out of a single piece of aluminum metal using a simultaneous 5-axis milling machine. For the purpose of this disclosure and the claims, when two parts are indicated as being formed “integrally”, it means that they are formed as a unit, such as would be the case, for example, if the parts were machined out of a single piece of metal. To obtain the requisite functionality of the tooling, conventional tooling is balanced and made concentric and operated at relatively high speeds, up to 46,000 RPM.

Once a person of ordinary skill in the art is made to recognize that a simultaneous 5-axis milling machine, with improved tooling as indicated above, can be made to machine molds as contemplated herein, the actual machining operation is a matter of routine application of known principles, and as such, is not detailed herein. Similarly, it will be understood that the mold halves of the present invention include elements such as conduits for receiving coolant and threaded bores for securing the mold halves to the molding machine, which elements are also not described in view of their routine nature.

One requirement of one-piece mold-making which may not be readily appreciated by persons of ordinary skill is the requirement for venting. Whereas mold halves of the prior art are normally not airtight, by virtue of the interstices or voids that form between adjacent parts as a consequence of the multi-part construction, one-piece molds have the potential to be relatively air tight which, all things being equal, would result in incomplete expansion of the parison. To ensure complete expansion, it is necessary to provide ventilation in the mold. The inventors have found that small holes, 0.003″-0.004″ in diameter, provide suitable ventilation, and leave no obvious marks on the molded article.

Whereas the product shown in FIGS. 5-8 includes as characteristics an integral threaded finish, a push-up base and an embossed feature, it should be understood that the invention is not so limited, and without limitation, should be understood as encompassing products having only one or two of such characteristics, and could also encompass products having one or more of such characteristics provided by a machined portion of the substrate and one or more similar characteristics provided via one or more inserts.

Further, whereas the product shown in FIGS. 5-8 is described as being produced by trimming the product of FIG. 4, it should be understood that a separate trimming step is not always required.

Yet further, whereas the product of FIGS. 5-8 is indicated to be a prototype container, it should be understood that this is not required. The invention will have great advantage in prototyping, since it allows faster turnaround in terms of mold production and also reduces costs, which can be of enhanced importance in prototyping. However, the invention can be utilized for the manufacture of production molds. In this latter case, it may be useful to machine the mold halves out of metal harder than aluminum, such as steel or beryllium copper alloy, or to coat the wear edges of an aluminum mold with harder material after machining, or to define the wear edges with harder material, as discussed fully below.

As well, whereas the description contemplates extrusion blow molding, it should be understood that the invention can be employed in the context of stretch blow molding as well as injection blow molding. As well, whereas plastic is indicated as the material which is molded, other blow-moldable materials, such as aluminum, may be employed, in which case, a suitable material for the molds would be steel. It is contemplated that aluminum could also be used for the molds, if suitable accommodations were made for controlling the mold temperature.

Of course, routine changes in size and shape of the container can be made and the feature can be a logo, code, insignia, etc.

Further, whereas the feature is indicated to be embossed, it could also be debossed. Further, whereas the feature shown is defined partly be each mold half, it could be defined fully by only one of the mold halves. For greater certainty, for the purpose of this disclosure and the claims, where a feature is specified as being defined “collectively” by two parts, then that feature may be defined wholly by either part, or partly by each part. In the context of the definition of container main bodies, threaded finishes and push-up bottoms, “collectively” will typically contemplate the latter.

As well, whereas an extruded parison of plastic is mentioned specifically, it will be understood that the present invention is also useful in the context of articles produced from preforms, of plastic or aluminum, which are heated and expanded to occupy a mold a cavity.

Whereas in FIGS. 1-8, a mold half machined entirely out of a casting of aluminum alloy is contemplated, this is not necessary.

Thus, there can also be provided according to the invention a mold half comprising a mold body defined at least in part by a single piece of aluminum or aluminum alloy mold material comprising a cavity and a feature area and further comprising a layer of a metal-matrix composite (MMC) formed integrally therein at the feature area, the MMC comprising an aluminum-nickel alloy matrix having WC particles embedded therein.

There can also be provided a mold comprising two mold halves of the present invention mated to receive a molding substance.

There can also be a process of producing a mold half comprising: machining a single piece of aluminum or aluminum alloy mold material to provide a mold body comprising a cavity and a feature area, the feature area being of smaller dimension than required for the mold half; and integrally forming a layer of a metal-matrix composite (MMC) in the feature area to build up the feature area to at least a dimension required for the mold half, the MMC comprising an aluminum-nickel alloy matrix having WC articles embedded therein.

The feature area may be, for example, one or more of a pinch-off area, a bottle top, threads for a bottle cap, a bottle shoulder, moil or dome flash sections, a handle eye, a tail or bottom, a compression molded feature (e.g. a strengthening web, a sliding core) or a retractable insert. A layer of the MMC may be formed integrally in one, more or all of the feature areas.

The MMC layer can comprise an aluminum-nickel alloy matrix. For the aluminum part of the matrix, aluminum alloys are particular useful, for example Al 2024 all, Al 2124 all, Al 2219 T31 through T87, Al 6009 all, Al 6010 all, Al 6061 T4 through T6511, Al 7075 T6 through T7351, Al 7050 all and Al 7475 all. Al-12Si alloys are particularly preferred. Al-12Si alloys are identified in the art as Al 4047 and comprise aluminum alloyed with about 11-13 wt % (nominally about 12 wt %) silicon, based on total weight of the alloy. Embedded in the relatively soft aluminum-nickel alloy matrix are hard and wear resistant particles of a tungsten carbide (WC). The nickel in the aluminum-nickel alloy matrix may be alloyed with the aluminum alloy prior to embedding the tungsten carbide (WC) particles, or more preferably, during the embedding process. During the embedding process, a WC/Ni material may be used in which the nickel acts as a binder for the WC particles in the material. During the embedding process, the nickel is melted and dissolves in the aluminum alloy to form the aluminum-nickel alloy matrix while the WC particles are only partially melted and remain as hard particulates embedded in the matrix. The Ni that dissolves in the aluminum alloy interacts with the aluminum alloy to form intermetallics that further increase matrix hardness.

WC particles can be embedded in the matrix in any amount suitable to provide sufficiently greater wear resistance, strength and/or toughness at the feature areas to satisfactorily extend the working life of the mold. The amount of WC distributed in the matrix is preferably in a range of from about 5 wt % to about 50 wt %, based on the weight of the composite, more preferably about 10-40 wt %, for example about 20-35 wt %. The amount of nickel alloyed in the matrix of the composite is preferably in a range of from about 1.5 wt % to about 5.5 wt %, based on the weight of the composite, more preferably about 2.4-3.6 wt %, for example about 3 wt %.

The MMC layer has greater wear resistance, strength and/or toughness than the aluminum or aluminum alloy into which the MMC is integrally formed, thereby providing greater resistance to high pressures and mechanical stresses during the molding process when mold halves are closed together. Further, the MMC layer has good bonding and compatibility to the mold material so that the interface and surrounding areas will not induce crack or peel-off during the molding operation. The MMC has a similar coefficient of thermal expansion compared to the mold material, which reduces the likelihood of cracking or other damage to the mold half due to changes in temperature.

The mold material can comprise aluminum or an aluminum alloy. Some examples of suitable aluminum alloys include Al 2024 all, Al 2124 all, Al 2219 T31 through T87, Al 6009 all, Al 6010 all, Al 6061 T4 through T6511, Al 7075 T6 through T7351, Al 7050 all and Al 7475 all. It should be noted that all aluminum alloys are suitable for blow molds due to their excellent thermal properties but those with high strength and heat treated properties are generally chosen due to their improved wear, strength and thermal properties.

The MMC layer may be formed in the feature area by any suitable process. The MMC layer may be formed by adding the MMC material to, or by otherwise modifying the surface of, the mold body in the feature area. In some instances, it may be desirable to form the MMC layer in different feature areas using different processes. The process or processes used to add and/or modify the feature area are preferably very well controlled so that the features are accurately engineered at the desired locations and are integrally formed in the mold body, e.g. by metallurgical bonding. Preferably, the process has minimal effect on the mold material in order to reduce potential distortion and property deterioration of the mold body. The thickness of the MMC layer depends on the mold working conditions and the process used to create the layer. For example, thicknesses may be from about several nanometers to several tens of millimeters.

The present invention is well-suited for one-piece molds and mold halves, i.e. mold halves that are wholly defined by a single piece of aluminum or aluminum alloy. However, in some cases, the mold half may comprise an insert in one or more parts where it is not desired to integrally form an MMC layer.

In one exemplary embodiment of the invention, an MMC layer may be formed by first engineering a mold body in which feature area is machined to an undersized dimension, and then adding MMC material to the feature area to build up the feature to final dimension. In a variation of this embodiment, the feature area may be built up with MMC material beyond final dimension and then machined down to final dimension. Various processes may be used to form the MMC layer. Such processes include, for example, laser cladding, laser alloying, electron beam cladding, electron beam alloying, brazing, diffusion bonding, friction stir welding, laser assisted thermal spray, laser assisted cold spray, low heat input welding (e.g. micro plasma welding), aluminum anodizing, ion implantation, chemical vapor deposition, plasma enhanced physical vapor deposition, diffusion coating, plasma treating, electroplating and electroless plating. Laser cladding is a process that enables metallurgical bonding of MMC material to the mold body to build up a relatively thick layer of the MMC layer in the feature area. Compared to conventional welding, laser cladding involves much better control and much less heat input, which reduces distortion and property deterioration in the mold body. As a variation, laser alloying may be used to melt the surface layer of the mold body to permit addition of various alloying elements to enhance surface hardness and wear resistance in the feature area. In another variation, an electron beam may be used instead of or in addition to a laser as the heating source for cladding.

Compared to conventional molds with inserts made of hard and tough metals, the present invention preferably uses one-piece mold halves that eliminate or reduce the number of insert segments, which significantly simplifies mold design, reduces purchasing and inventory controls, simplifies manufacturing and simplifies assembling. As a result, molds of the present invention may be constructed relatively quickly and at lower cost. In addition, improved heat transfer/thermal management of the molds of the present invention is permitted through (a) eliminating thermal breaks between the inserts and mold bodies, (b) permitting construction of cooling channels at the original insert areas, and (c) enabling addition of low thermal conductive material at the top of the feature area to help to produce strong and even weld lines.

By building up and/or enhancing the feature areas with a specifically engineered MMC material, the specific requirements for each feature area can be met by tailoring the specifically engineered MMC material without affecting the material used to make mold bodies. Metallurgical bonding between the MMC material and the mold material offers good compatibility between the two materials, which ensures long life of the feature areas during high pressure and high cycle molding operations. As a result, the present invention permits mass production of molded articles.

Further, known molds having a very hard metal layer (such as steel, titanium, etc.) metallurgically bonded to a softer but very thermally conductive aluminum or aluminum alloy substrate, such as those described in European Patent Application EP 0742094A1 and the like, suffer from thermal incompatibility between the cladding layer and the mold body leading to cracking, thereby shortening the effective working life of the mold. The present molds combine wear resistance, strength and/or toughness with good thermal compatibility at the feature and wear areas to provide molds with significantly extended working lives.

Furthermore, the present invention may be used not only on flat parting surfaces but may also be advantageously used on contoured parting surfaces. There is no restriction on mold size, the present molds being applicable to both large and small size molds. Molds of the present invention may be used for any molding process, for example, blow molding, injection molding and compression molding. The present invention is particularly useful for blow molding processes. The present invention is particularly useful for molding of plastics, particularly thermoplastics.

The present invention may be used to produce any article that may be formed using a molding process. Some examples of articles include containers (e.g. bottles), automotive components, recreational components, industrial components and chemical components, especially containers.

Further features of the invention will be described or will become apparent in the course of the following detailed description.

FIGS. 9-11 depict one embodiment of a one-piece blow mold half for a bottle blow mold in accordance with the present invention at various stages of fabrication. Referring to FIG. 9, one-piece blow mold half 150 comprising aluminum alloy mold body 151 and cavity 152 is pre-machined to an undersized shape at pinch-off area 153, thread feature area 156, bottle top feature area 157 and shoulder feature area 159. Referring to FIG. 10A, in order to complete the mold half, a layer of MMC material is laser clad at pinch-off area 153 (and the other feature areas not shown in FIG. 10) to provide a raised layer 170 of the cladding material having excess portion 171. In order to avoid undercut and/or mismatch, mold body 151 at each side of raised layer 170 is rough machined prior to the laser cladding step to leave spare layer 172 of mold material at each side of raised layer 170. After the cladding step, spare layer 172 is machined off along with excess portion 171 of the cladding material to bring mold body 151 and raised layer 170 to final dimension (FIG. 10B). For certain processes, the spare layer may not be necessary provided no undercut and/or mismatch between the MMC material and the mold body occurs. Referring to FIG. 11, after cladding, one-piece blow mold half 150, having mold body 151 and cavity 152, comprises clad pinch-off area 155 and clad other feature areas 158, 160 and 163 in which an MMC layer is integrally formed.

Example 1 Laser Cladding of Al 7075-T651 Substrate with Al 4047+WC/Ni

Laser cladding was performed by using a focused Nd:YAG laser beam with a 115-mm focal length lens. A powder feeder was used to simultaneously deliver Al 4047 and WC/Ni powder mixture through a feed nozzle into the melt pool at a rate of about 2 g/min. The laser beam and powder feeding nozzle were kept stationary, while the Al-7075-T561 substrate was moved under the beam by a CNC motion system. The cladding was conducted with an average laser power up to 500 W with a beam diameter of about 1 mm. A laser pulse duration of 10 ms and a frequency of 10 Hz were used for the processing. An overlap ratio of 30% was used between passes to produce multi-passes to cover the required area, while a z movement of about 130 μm was used to deposit multi-layers to reach the required height.

Example 2 Microstructure Analysis of Clad Substrates

In a preliminary experiment, a layer of Al 4047 (which is the matrix material of the metal-matrix composite) was laser clad on to Al 7075-T651 substrate by a modification of the procedure of Example 1 in order to examine the microstructure of the clad specimen. This was compared to a similar specimen in which a layer of Al 7075 was clad on to Al 7075-T651 substrate. Examination by optical microscopy of a cross-section of the specimens showed that cladding with Al 7075 showed a tendency for cracking while cladding with Al 4047 produce a good metallurgical bond without inducing cracks or pores in the clad layer. Further, the laser clad Al 4047 layer showed good machinability, a smooth transition of hardness from the substrate to the clad layer, and a generally uniform hardness through the layer. Finally, a polishing test showed that the laser clad Al 4047 layer is superior to the Al 7075-T651 substrate in polishing.

With reference to FIG. 12, microstructure analysis was extended to a metal-matrix composite (MMC) in which Al 4047+30% (90% WC+10% Ni) MMC layer 200 was laser clad on to Al 7075-T651 substrate 201 in accordance with the process in Example 1. The MMC comprises WC particles embedded in an Al 4047/Ni matrix formed using 30 wt % WC/Ni material. The WC/Ni material consists of 90 wt % WC (tungsten carbide) and 10 wt % Ni (nickel). Thus, the amount of WC in the MMC layer is about 27 wt % and the amount of nickel alloyed with the Al 4047 is about 3 wt %, based on the weight of the MMC. A good metallurgical bond was formed with no formation of cracks or pores in the MMC layer. Further, in the MMC layer, WC hard particles 202 were evenly distributed in Al 4047/Ni matrix 203, while the Ni from the WC/Ni material dissolved in the Al 4047 to form intermetallics that further increase matrix hardness. Similar experiments were performed with other metal-matrix composites, i.e. Al 4047+Al₂O₃ and Al 4047+WC/Co. In the case of Al 4047+Al₂O₃, laser cladding did not generate hardening, probably due to the decomposition of Al₂O₃ during the cladding process. In the case of Al 4047+WC/Co, the clad layer had improved wear resistance but showed a tendency to crack.

Example 3 Microhardness Analysis of Clad Substrates

A Vickers hardness test (ASTM E384—10e2) was conducted on the laser clad product of Example 1 using a load of 500 g for 15 s at evenly distributed points spaced by 0.2 mm FIG. 13 depicts hardness depth profile of the Al 4047+30% (90% WC+10% Ni) MMC layer clad on the Al 7075-T651 substrate. It is evident from FIG. 13 that the Al 4047+30% (90% WC+10% Ni) is harder than the Al 7075-T651 substrate. The substrate near the clad layer has a softening zone with a Vickers hardness (Hv0.5) of around 140, perhaps due to annealing induced by laser cladding. There was a larger deviation in the hardness of laser clad (Al 4047+30% (90% WC+10% Ni)) layer due to heterogeneous features in the MMC.

Further, with reference to FIG. 14, Vickers hardness of the Al 4047+30% (90% WC+10% Ni) MMC layer was compared to that of the Al 7075-T651 and other typical mold insert materials (i.e. A2 steel, Be—Cu alloy and Stainless Steel Stavex ESR). Table 1 summarizes the results. Table 1 and FIG. 14 demonstrate that the Al 4047+30% (90% WC+10% Ni) layer is harder than Al 7075-T651 and approaches that of the steels.

TABLE 1 Vickers Hardness Material Vickers Hardness (Hv0.5) A2 steel 222 Be—Cu alloy 384 Stainless Steel Stavex ESR 231 Al 4047 + 30% (90% WC + 10% Ni) 198 Al 7075-T651 177

Example 4 Wear Resistance Analysis of Clad Substrates

Wear resistance was performed with pin-on-disc testing as per ASTM G99-05 (2010) to evaluate sliding wear resistance of a laser-clad specimen of the present invention (Al 4047+30% (90% WC+10% Ni) on Al 7075-T651) in comparison to Al 7075-T651, A2 steel, Be—Cu and Stainless Steel Stavex ESR The test was performed with a Falex Pin-on-Disc Tester with a dry slide to determine volume wear loss. All sample surfaces were fine ground and cleaned before testing. The testing was done with a normal load of 3.5 N, at a linear slide speed of 300 mm/s over a total slide distance of 1500 m using a ¼″ tungsten carbide (WC) ball.

Wear loss results from the pin-on-disc testing are shown in FIG. 15 and summarized in Table 2. Using wear of Al 7075-T651 substrate as a reference, relative wear resistance (R) was calculated by dividing volume wear loss of Al 7075-T651 by volume wear loss of the other materials. Wear resistance of the clad Al 4047+30% (90% WC+10% Ni) in accordance with the present invention is significantly better (5.28 times) than that of the Al-7075-T651 substrate. The wear resistance of the Al 4047+30% (90% WC+10% Ni) layer is similar to that of Stavex Stainless Steel. The wear resistance of the Al 4047+30% (90% WC+10% Ni) layer is close to but still relatively inferior to that of Be—Cu.

TABLE 2 Wear Loss Volume Wear Loss Relative Wear Material (10⁻³ mm3/m) Resistance (R) A2 steel 0.085 17.1 Be—Cu alloy 0.157 9.27 Stainless Steel Stavex ESR 0.251 5.80 Al 4047 + 30% (90% WC + 10% 0.276 5.28 Ni) Al 7075-T651 1.456 1

Cladding of an aluminum or aluminum alloy substrate with a Al 4047+30% (90% WC+10% Ni) metal-matrix composite provides an excellent balance of properties for molding, especially blow molding, applications. The clad metal-matrix composite layer forms a good metallurgical bond with the substrate with no formation of cracks or pores. Excellent hardness and wear resistance, approaching that of hard materials used in the prior art, leads to extended life at feature areas of the mold, while good thermal compatibility between the substrate and metal-matrix composite layer makes the MMC layer less prone to cracking further extending the life of the mold. Good machinability provides for ease of manufacturing.

In contrast, Al 7075-T651 itself is soft and easily worn, therefore its use at feature areas in one-piece molds results in reduced service life of the molds. Use of typical hard, wear resistant materials such as steels and Be—Cu alloy at feature areas extends working life of aluminum or aluminum alloy molds, but is still unsatisfactory since thermal incompatibility leads to cracking which prevents a full realization of the benefits of the harder material. Further, such hard, wear resistant materials are difficult to machine, which makes manufacturing more difficult.

Other advantages that are inherent to the structure are obvious to one skilled in the art. The embodiments are described herein illustratively and are not meant to limit the scope of the invention as claimed. Variations of the foregoing embodiments will be evident to a person of ordinary skill and are intended by the inventor to be encompassed by the following claims. 

1. A blow mold comprising: a pair of mold halves having an operative configuration wherein said mold halves together define a cavity for a container, the container having a main body and a characteristic selected from the group of characteristics consisting of: a push-up base; an integral finish; and an embossed or a debossed feature, wherein each of the pair of mold halves has a first portion and a second portion formed integrally with the first portion; when the pair of mold halves is in the operative configuration, the first portions collectively define the main body and the second portions collectively define the characteristic; and at least one of the pair of mold halves has a relatively soft substrate portion and a relatively hard surface layer formed integrally with the substrate portion.
 2. A mold according to claim 1, wherein the substrate portion is an aluminum alloy and the surface layer is a metal-matrix composite (MMC).
 3. A mold according to claim 2, wherein the MMC comprises an aluminum-nickel alloy matrix having WC particles embedded therein.
 4. A mold according to claim 3, wherein the WC particles are distributed in the aluminum-nickel alloy matrix in an amount in a range of from 5 wt % to 50 wt %, based on the weight of the composite.
 5. A mold according to claim 3, wherein the WC particles are distributed in the aluminum-nickel alloy matrix in an amount in a range of from 10 wt % to 40 wt %, based on the weight of the composite.
 6. A mold according to claim 3, wherein the WC particles are distributed in the aluminum-nickel alloy matrix in an amount in a range of from 20 wt % to 35 wt %, based on the weight of the composite.
 7. A mold according to claim 3, wherein the WC particles are distributed in the aluminum-nickel alloy matrix in an amount of about 27 wt %, based on the weight of the composite.
 8. A mold according to claim 4, wherein the aluminum-nickel alloy matrix comprises Al-12Si alloy alloyed with nickel.
 9. A mold according to claim 8, wherein the MMC comprises 1.5-5.4 wt % Ni, based on weight of the composite.
 10. A mold according to claim 8, wherein the MMC comprises 2.4-3.6 wt % Ni, based on weight of the composite.
 11. A mold according to claim 8, wherein the MMC comprises 3 wt % Ni, based on weight of the composite.
 12. A mold according to claim 9, wherein the aluminum alloy is selected from Al 2024 all, Al 2124 all, Al 2219 T31 though T87, Al 6009 all, Al 6010 all, Al 6061 all, Al 6061 T4 through T6511, Al 7075 T6 through T7351, Al 7050 all or Al 7475 all.
 13. A mold according to claim 9, wherein the aluminum alloy comprises Al 7075-T6 through T7351.
 14. A mold according to claim 9, wherein the aluminum alloy is Al 7075-T651.
 15. A process of producing a mold half comprising: applying a layer of a metal-matrix composite (MMC) to a piece of machined aluminum alloy to form a composite structure; and machining the composite structure.
 16. A process according to 15, wherein the MMC is an aluminum-nickel alloy matrix having WC particles embedded therein.
 17. A process according to claim 16, wherein the MMC layer is formed by laser cladding.
 18. A process according to claim 17, wherein the WC particles are distributed in the aluminum-nickel alloy matrix in an amount in a range of from 20 wt % to 35 wt %, based on the weight of the composite; the aluminum-nickel alloy matrix comprises Al-12Si alloy; the MMC comprises 1.5-5.4 wt % Ni, based on weight of the composite; and the aluminum alloy is Al 7075-T6 through T7351.
 19. A process according to claim 18, wherein the composite structure is machined into the mold half.
 20. A process according to claim 18, wherein one or more inserts are secured to the machined composite structure to form the mold half. 